Ecology and Symbiosis: Key Concepts for Biology Students

Symbiosis

Intimate, long-term association between species.

Types of symbiosis

Mutualism, Commensalism, Parasitism.

Commensalism examples

Cattle egrets, epiphytes, burdock seeds.

Endoparasites

Parasites living inside the host.

Ectoparasites

Parasites living on the surface of the host.

Brood parasitism

Cowbirds or cuckoos laying eggs in other species' nests.

Brood parasitism consequence

Leads to egg mimicry in cuckoos.

Holoparasite

Fully parasitic plant with no photosynthesis.

Hemiparasite

Plant that is partly parasitic but still photosynthesizes.

Wolbachia

Parasitic bacteria that can increase host fecundity over time.

Mycorrhizae

Mutualistic in nutrient-poor soils; parasitic in nutrient-rich soils.

Obligate mutualism

Partners require each other to survive (lichens, corals).

Facultative mutualism

Partners benefit but don't need each other (generalist pollinators).

Ecological consequences of mutualisms

Form community foundations, aid regrowth, expand ranges.

Serial Endosymbiotic Theory

Organelles evolved from engulfed bacteria (Lynn Margulis).

Types of competition

Consumption, Preemption, Interference, Territorial.

Competitive Exclusion Principle

Two species cannot share identical niches indefinitely.

Fundamental niche

Full potential range a species could use.

Realized niche

Actual range after competition restricts it.

Niche partitioning

Species divide resources to reduce competition.

Character displacement

Traits diverge where species overlap.

Consequences of competition

Competitive release and character displacement.

Organismic community

Communities seen as predictable and tightly linked.

Individualistic community

Communities are loose associations of species.

Habitat diversity

More habitat types increase species richness.

Keystone species

Species with disproportionate impact on community.